Optimization of extraction process of propolis flavonoids by response surface methodology and its antioxidant activity research

Propolis flavonoids were extracted by ethanol,and the extraction process was optimized by response surface analysis.On the basis of one-factor-at-a-time experiment,optimal extraction conditions for maximizing popolis flavonoids were determined by using a 4-variable,3-level Box-Behnken experimental design combined with response surface analysis as follows:the liquid-material ratio was 14:1(mL·g-1),the extraction temperature was 72.6℃,the extraction time was 2.5h,the ethanol concentration was 80%(v/v),resulting in an propolis flavonoids yield of 33.82%,which was basic agreement with the predicted value of 33.9324%.Thus,the optimal process was reliable.The antioxidant activity in vitro condition of propolis flavonoids were evaluated by DPPH free radical scavenging assay and potassium ferricyanide reduction assay using V C as the control.Propolis flavones were found to have powerful DPPH free radical scavenging capacity and reducing power.Thus,propolis flavonoids could be developed as excellent natural antioxidant resources.